On the growth of northern shrimp Pandalus eous in the waters off noto peninsula, the sea of Japan

Abstract

The growth pattern of the Northern Shrimp was made clear by tracing size composition of the dominant year class and spawning interval, and the following results were obtained. Most of the northern shrimp change sexes from male to female at 5 years old. In the female stage they spawn eggs every other year and make the first hatch of the larvae at 7 years old. The number of spawning times was estimated to be more than three. So the life span of the Northern Shrimp was estimated to be longer than 11 years. The growth rate is low, and the life span is long as compared with those obtained so far. Growth formula was determined as lt=34.15[1-exp {-0.252 (t+0.016)}], where lt represents carapace length in mm at age t in years. The Northern Shrimp of the Sea of Japan is inhabited in the most southern region. However the growth rate of the species is low as compared with other areas. This is due to the fact that the living water temperature is very cold.